Crimping blade profile

ABSTRACT

The invention relates to a crimping blade with a profile such that the angle of attack β of the sheet metal to be crimped remains constant during the entire crimping phase. In this way, the force applied to the sheet metal is always at the same angle in relation to the sheet metal.

The invention concerns crimping tools and more particularly thepre-crimping blade that equips said tools. The crimping system comprisesa matrix on which is placed the metal sheet(s) to be crimped, apre-crimping blade and a crimping blade that come successively to pushon the edge of the metal sheet so as to raise it and fold it down.

There are several types of crimping:

-   -   “flat” crimping,    -   “water drop” crimping, which is characterized by the fold of the        crimped metal sheet having the shape of a “water drop”.

Flat crimping is a crimping operation whereby the part to be crimped isfolded flat.

Water drop crimping is advantageous to reinforce the edge of the part,by creating a shape of a tube having a high inertia. It makes itpossible to manufacture parts, such as the front or the rear of carhoods, whose profile is visible by the conductor. The hoods must indeedbe the least aggressive possible in the case of an accident.

Blade profiles at 45° and radial blade profiles are known, but thesetypes of blades do not allow a perfect mastering of the crimpingoperation and present a risk that the blade may be raised from thematrix. This phenomenon generates a defect of double line, if theelastic limit is exceeded, which is unaesthetic.

The object of the present invention is to propose a pre-crimping bladewhich makes it possible to perform a pre-crimping with metal sheetsforming an opening angle more important, beyond 107°, and to master thefolding radius of the metal sheet during the pre-crimping phase.

If the angle of attack β is defined as the angle formed by the edge ofthe blade and the tangent to the blade profile.

The pre-crimping blade according to the invention has a profile suchthat the angle of attack β of the metal sheet to be crimped remainsconstant during the whole pre-crimping phase. Thus, the force applied tothe metal sheet has always the same angle relative to the metal sheet.

The blade profile according to the invention is calculated by thefollowing formula (1):

${y\; n} = {L + {\sum\limits_{0}^{n}\frac{\begin{matrix}{{R\left\lbrack {{- {\cos\left( {\theta\; n} \right)}} - {\sin\left( {\theta\; n} \right)} + {\cos\left( {{\theta\; n} - 1} \right)} + {\sin\left( {{\theta\; n} - 1} \right)}} \right\rbrack} +} \\{\left. {{L\left\lbrack {\sin\;\theta\; n} \right)} - {\sin\left( {{\theta\; n} - 1} \right)}} \right\rbrack +} \\{R\;{m\left\lbrack {{{- \theta}\;{n \cdot {\sin\left( {\theta\; n} \right)}}} + {\theta\; n} - {1 \cdot {\sin\left( {{\theta\; n} - 1} \right)}}} \right\rbrack}}\end{matrix}}{\tan\left( {\beta + {\theta\; n} - 1} \right)}}}$

-   where R is the outer crimping radius.-   e is the thickness of the metal sheet to be crimped.-   Rm=R−e/2-   θ is the folding angle of the metal sheet, θn are the various angle    values taken by the edge of the metal sheet between the start of the    pre-crimping operation and the end of the crimping operation, i.e.,    between 0 and the opening angle of the metal sheet, thus, for    example, π/2 is the metal sheet is open at 90°. If α, the value of    the opening angle at the start, is above 90°, θn will vary between    π/2-α and α.-   β is the angle of attack of the metal sheet, i.e., the angle formed    by the edge of the metal sheet and the tangent to the crimping blade    at the point of contact of the latter with the outer edge of the    metal sheet.-   L is the height of the edge to be crimped.

According to another characteristic of the invention, the angle β iscomprised between 40° and 60°. In this range of values, the forceapplied to the metal sheet enables a better folding of the latter overitself.

According to a specific characteristic of the invention, the angle β isabout 53°. This angle is the optimum angle that makes it possible tofold the metal sheet without raising it from the matrix.

According to another characteristic of the invention, the blade pusheson the outer point of the edge of the metal sheet. The resulting forcefrom the efforts generated by the blade is concentrated toward theoutside of the part to be crimped, thus limiting plastic deformations.

According to a specific characteristic of the invention, thepre-crimping operation is performed on a metal sheet forming an angleopen at more than 107°. The difficulty reside in that it is difficult topre-crimp metal sheets forming an angle of more than 90°, the bladeaccording to the invention makes it possible to perform a pre-crimpingoperation on metal sheets forming an angle open at more than 107°.

According to another specific characteristic of the invention, thepre-crimping operation is performed on an aluminum sheet. Aluminum is asuppler material than metal sheet and is thus more subject to the doubleline defect.

The invention will be better understood by reading the followingdescription which is provided as an example only and is made inreference to the annexed drawings in which:

FIG. 1 is a side view of the blade according to the invention,

FIG. 2 is a schematic view showing the developed trajectory of the edgeof the metal sheet.

As is visible on FIG. 1, the pre-crimping blade 1 and the matrix 2constitute the crimping machine. The metal sheet to be crimped 3 such asa vehicle body skin, is placed on the matrix 2, a second metal sheet 4such as a double is placed on the metal sheet to be crimped 3.

The pre-crimping blade 1 follows a descending movement to come closer tothe matrix 2 and fold the metal sheet 3.

The outer edge 30 of the metal sheet 3 is in contact with the profile 10of the blade 1. Along with the descending movement of the blade 1following a trajectory that is rectilinear and substantiallyperpendicular to the matrix, the edge 30 slides on the profile 10following a trajectory 32, which performs the folding operation on themetal sheet 3.

As is visible on FIG. 1, the profile 10 of the blade 1 is remarkable inthat the plane 34 of the edge 30 always forms an angle β with thetangent to the profile 10 of the blade 1, whichever the position of theedge 30 relative to the blade 1. In this FIGURE, the angle α of themetal sheet 3 at the start is above 90°, but it can also be above 107°up to about 120°.

At the end of the pre-crimping operation, the metal sheet to be crimped3 is parallel to the matrix 2 and the crimping operation will beperformed by a crimping blade which will contact the metal sheet 3 withthe metal sheet 4 as is made visible by dotted line on FIG. 1.

FIG. 2 details the various parameters of the trajectory of the edge 30of the metal sheet 3.

If one considers that the neutral fiber 33 is not subjected toelongation, its trajectory depends on the height of the edge to becrimped L, of a center of rotation O, and of the radius of curvature θthat one wishes to obtain.

Then, to define the trajectory 32 of the edge 30, it is necessary to addthe thickness e of the metal sheet as an additional parameter.

The trajectory of the edge 30 of the metal sheet 3 is given by the pointhaving the coordinates (x,y) such that:x=R(1−cos(θ))+(L−R−(Rm.θ)).sin(θ)y=R.sin(θ)+(L−R−(Rm.θ)).cos(θ)+R

Once the trajectory 32 has been defined, the profile 10 of the blade 1is calculated by choosing the angle of attack β relative to the neutralfiber 33 or to the edge 30 as a function of the formula (1) given above.This angle of attack β is selected to be preferably approximately 53°.

The trajectory of the blade 1 is rectilinear perpendicular to the matrixand the resulting force of the efforts generated by the latter isconcentrated towards the outside of the part to the crimped 3, thuslimiting the plastic deformations.

The profile of the blade thus defined makes it possible to pre-crimpdoors as well as hoods, covers, made of steel or aluminum, whilesimplifying the edge flanging operations.

1. Pre-crimping blade for crimping a metal sheet having a profilewherein the profile is such that an angle of attack β of the metal sheetto be crimped remains constant when the blade pushes on an edge of themetal sheet rectilinearly such that the edge of the metal sheet slideson the profile following a trajectory, which performs a foldingoperation on the metal sheet, wherein the angle β is comprised between45° and 60°.
 2. Pre-crimping blade according to claim 1 wherein theangle β is about 53°.
 3. Pre-crimping blade according to claim 1,wherein the pre-crimping is performed on a metal sheet forming an angleopen at more than 107°.
 4. Pre-crimping blade according to claim 1,wherein the pre-crimping is performed on an aluminum sheet. 5.Pre-crimping blade according to claim 2, wherein the blade pushes on anouter point of an edge of the metal sheet.
 6. Pre-crimping bladeaccording to claim 2, wherein the pre-crimping is performed on a metalsheet forming an angle open at more than 107°.
 7. Pre-crimping bladeaccording to claim 2, wherein the pre-crimping is performed on analuminum sheet. is performed on a metal sheet forming an angle open atmore than 107°.
 8. Pre-crimping blade according to claim 1, wherein theblade pushes on an edge of the metal sheet perpendicularly to a matrixon which the metal sheet is placed.
 9. Pre-crimping blade according toclaim 1, wherein the blade pushes on the metal sheet rectilinearlyduring the whole pre-crimping phase.
 10. Pre-crimping blade for crimpinga metal sheet having a profile wherein the profile is such that an angleof attack β of the metal sheet to be crimped remains constant when theblade pushes on the metal sheet rectilinearly, wherein the profile ofthe blade is calculated with the following formula:${y\; n} = {L + {\sum\limits_{0}^{n}\frac{\begin{matrix}{{R\left\lbrack {{- {\cos\left( {\theta\; n} \right)}} - {\sin\left( {\theta\; n} \right)} + {\cos\left( {{\theta\; n} - 1} \right)} + {\sin\left( {{\theta\; n} - 1} \right)}} \right\rbrack} +} \\{\left. {{L\left\lbrack {\sin\;\theta\; n} \right)} - {\sin\left( {{\theta\; n} - 1} \right)}} \right\rbrack +} \\{R\;{m\left\lbrack {{{- \theta}\;{n \cdot {\sin\left( {\theta\; n} \right)}}} + {\theta\; n} - {1 \cdot {\sin\left( {{\theta\; n} - 1} \right)}}} \right\rbrack}}\end{matrix}}{\tan\left( {\beta + {\theta\; n} - 1} \right)}}}$ whereinR is the outer crimping radius, e is the thickness of the metal sheet tobe crimped, Rm=R−e/2, θ is the folding angle of the metal sheet, β isthe angle of attack of the metal sheet, and L is the height of the edgeto be crimped.
 11. Pre-crimping blade according to claim 10, wherein theangle β is comprised between 45° and 60°.
 12. Pre-crimping bladeaccording to claim 11, wherein the angle β is about 53°. 13.Pre-crimping blade according to claim 10, wherein the blade pushes on anouter point of an edge of the metal sheet.
 14. Pre-crimping bladeaccording to claim 10, wherein the pre-crimping is performed on a metalsheet forming an angle open at more than 107°.
 15. Pre-crimping bladeaccording to claim 10, wherein the pre-crimping is performed on analuminum sheet.
 16. Pre-crimping blade for crimping a metal sheet havinga profile wherein the profile is such that an angle of attack β of themetal sheet to be crimped remains constant when the blade pushes on anedge of the metal sheet rectilinearly such that the edge of the metalsheet slides on the profile following a trajectory, which performs afolding operation on the metal sheet, wherein the blade pushes on anouter point of an edge of the metal sheet.
 17. Pre-crimping bladeaccording to claim 16, wherein the pre-crimping is performed on a metalsheet forming an angle open at more than 107°.
 18. Pre-crimping bladeaccording to claim 16, wherein the pre-crimping is performed on analuminum sheet.
 19. Pre-crimping blade for crimping a metal sheet havinga profile wherein the profile is such that an angle of attack β of themetal sheet to be crimped remains constant when the blade pushes on anedge of the metal sheet rectilinearly such that the edge of the metalsheet slides on the profile following a trajectory, which performs afolding operation on the metal sheet, wherein the profile of the bladeis defined wherein the folding operation is performed on a metal sheetforming an angle of more than 90 degrees before folding to an angle ofless than 90 degrees after folding.
 20. Pre-crimping blade according toclaim 19, wherein the angle β is comprised between 45 and
 60. 21.Pre-crimping blade according to claim 19, wherein the blade pushes on anouter point of an edge of the metal sheet.
 22. Pre-crimping bladeaccording to claim 19, wherein the pre-crimping is performed on a metalsheet forming an angle open at more than 107°.
 23. Pre-crimping bladeaccording to claim 19, wherein the pre-crimping is performed on analuminum sheet.